ROSAT observations of the SIGMA source GRS 1227 + 025 near 3C 273

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Abstract
In an observation in the 40–80 keV band with the SIGMA instrument on the Russian GRANAT satellite in which the quasar 3C 273 was not detected at > 2.5σ significance, another source, GRS 1227 + 025, was detected at 5.5σ significance close to the position of 3C 273. If GRS 1227 + 025 is a separate source to 3C 273, then its presence will cause confusion in the determination of the flux at high energies of 3C 273, which is one of the most widely observed extragalactic objects and the testbed for many theories of active galactic nuclei (AGN). The reality of GRS 1227 + 025 as a separate source to 3C 273 would be strengthened if a realisticcounterpart could be found in other high-energy observations. We have therefore searched a very deep ROSAT Position Sensitive Proportional Counter (PSPC) observation (0.1–2.4 keV) in which 3C 273 is the dominant source and have discovered three very faint sources in the SIGMA error circle of GRS 1227 + 025, one of which corresponds to a previously suggested counterpart found in observations with the Einstein observatory. However, X-ray spectral and timing analysis shows that none of these is a likely identification of GRS 1227 + 025. We conclude that, if real, GRS 1227 + 025 must represent a transient event or be very highly obscured (NH ≥ 1024 cm2).

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